THE MECHANISM OF CRACK EXTENSION IN NON-UNIFORM ROCK

A clear understanding of the extension of hydraulic fractures on the sandstone-mudstone boundary is the key issue of effectively developing the thin and poor reservoir. In order to simulate the extension property of the fractures on the sandstone-mudstone boundary, with ABAQUS as a platform, the fracture extension process on the sandstone-mudstone boundary is simulated using the separated fracture model with the extended finite element framework. A preset virtual node method is proposed, to make the fracture extension independent of the grid boundary and the extension evolution on the sandstone-mudstone boundary is obtained through the introduction of additional enhancements in the interpolation function of displacement. The fracture extension on the low permeability reservoir sandstone-mudstone boundary is also tracked in real-time by using the white light speckle experiment. The extension process is in good agreement with the numerical simulation, which indicates that the extended finite element method is an effective means of quantitative analysis for fracture extension, and the fracture extension process on the boundary is also studied.